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%I #12 Jun 18 2013 06:06:14
%S 3,12,21,27,30,39,47,57,66,69,84,93,102,111,114,120,129,139,156,166,
%T 174,183,189,192,207,216,219,225,237,243,252,264,270,273,282,290,309,
%U 318,327,336,351,354,363,380,386,398,407,416,425,437,443,462,471,480
%N Positions of occurrences of 2,1,1,2,1 in the Kolakoski sequence A000002.
%H Nathaniel Johnston, <a href="/A074276/b074276.txt">Table of n, a(n) for n = 1..10000</a>
%e The Kolakoski sequence begins 1,2,2,1,1,2,1,2,2,1,2,2,1,1,2,1,..., so 2,1,1,2,1 occurs at positions 3 and 12.
%t a2 = {1, 2, 2}; Do[a2 = Join[a2, {1 + Mod[n - 1, 2]}], {n, 3, 400}, {i, 1, a2[[n]]}]; a2 //. {a___, 2, 1, 1, 2, 1, b___} :> {a, 0, 1, 1, 2, 1, b} // Flatten // Position[#, 0] & // Flatten (* _Jean-François Alcover_, Jun 18 2013 *)
%Y Cf. A074275, A074277.
%K nonn,easy
%O 1,1
%A _Jon Perry_, Sep 21 2002
%E Extended and offset corrected by _Nathaniel Johnston_, May 02 2011
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